Zyzyfer is probably right. It's sounding to me that you made the mistake of not kowtowing to one of the kids. Even telling the little darlings to apologize is considered harsh discipline to a kid who's never been told to stop before.

I'm suprised that nobody has asked you this yet, but here goes:
How far are you into your contract?
You mentioned that the arguement with the coworker was "6 months ago", so you are at least halfway through, right?
Maybe they don't want to pay you your bonus (as well as return airfare if it wasn't prepaid).........

they're probably considering that they don't have another teacher coming right now, so they'd like you to stay till the new person comes, and they are trying to see how to best force you to do their bidding.

and if you disagree, they will probably threaten to not give you a letter of release, or something to that effect.

Play hardball. Outline why you are leaving, and why the atmosphere forced you to take that course of action. and be polite, but firm on that point. probably you'll come out on top.

Who can say what is normal? It sounds to me like that's what they wanted.
I think William is right on with his comments. I have only been here a year and a half, but what I have experienced here is very similar to what William describes. It's sad, but true.
Funny, I am just about to reach the 6 month point in my contract and am thinking of handing in my notice as well. It just ain't worth it any more!
I feel for you.
Some waygug-in

Still nothing today, but lots of arguments between the supervisor and manager it seems.
I plan to play hard ball but at the moment they haven't even acknowlegded that I have handed the request in! Should I approach them about or let them come to me?
Seriously I'm about ready to bolt. It's so passive-agressive at the moment. I just want to know where I stand.